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Custom Software and Client Portal for an Accounting Firm 2026 (London)

Mohamed Bah·Fondateur, Kolonell
September 4, 2026
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Custom Software and Client Portal for an Accounting Firm 2026 (London)

Custom Software and Client Portal for an Accounting Firm 2026 (London)

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The verdict in three sentences

A custom client portal turns document collection from an endless chase into a structured, timestamped flow, cutting collection time by 40% and making file completion far more reliable. For a firm of 8 to 20 staff, budget 25,000 to 60,000 EUR for the portal and document management, plus 8,000 to 18,000 EUR to connect your production tool (Cegid, IRIS, or equivalent). The investment pays back in 12 to 24 months through time saved and the capacity to take on more files with the same headcount.

What the budget actually covers

A firm is not buying "a website" but a chain: client uploads, automatic filing into document management, e-signature, scheduled reminders, and a feed into production. Here are the 2026 ranges for a differentiating build.

Functional block2026 range (EUR)Indicative timeline
Client portal + upload space12,000 – 22,0004 – 6 weeks
Document management with auto-filing8,000 – 18,0003 – 5 weeks
Integrated e-signature4,000 – 9,0002 – 3 weeks
Automatic reminders (email + SMS)3,000 – 7,0001 – 2 weeks
Production connection (Cegid / IRIS)8,000 – 18,0003 – 6 weeks
Full project total35,000 – 74,00010 – 16 weeks

On top of this comes application maintenance of 300 to 800 EUR/month depending on the number of users and the support level expected.

Vendor module or custom build: the real trade-off

Software vendors offer portals bundled with their suite. They activate fast but are standardised: you adapt your firm to the tool, not the reverse. Custom becomes worthwhile once your workflow is a competitive edge.

CriterionVendor moduleCustom build
Upfront cost0 – 5,000 EUR + subscription35,000 – 74,000 EUR
Recurring cost15 – 40 EUR/user/monthMaintenance 300 – 800 EUR/month
Workflow customisationLowTotal
Brand and client experienceGenericYour colours
Bespoke integrationsLimitedUnlimited
Vendor lock-inHighNone

For a 30-staff firm, vendor subscriptions can reach 10,000 to 14,000 EUR/year. Over five years the gap narrows sharply in favour of custom, which becomes an asset of the firm.

Mini case study

Claire runs a 14-staff accounting firm in London. Her managers spend on average 5 hours per file per year chasing and filing documents, across 220 files annually, or 1,100 hours. The custom portal, billed at 48,000 EUR plus 500 EUR/month maintenance, cuts this by 40%, freeing 440 hours per year. At a loaded hourly cost of 45 EUR, annual savings reach 19,800 EUR, a payback of roughly 24 months — before counting the extra files absorbed at constant headcount.

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FAQ

How much does a client portal for an accounting firm cost in 2026?

Budget 25,000 to 60,000 EUR for the portal and document management, excluding production connection. A full build with signature and reminders sits around 35,000 to 74,000 EUR.

Can the portal connect to Cegid or IRIS?

Yes, via API or a file-exchange gateway. Budget 8,000 to 18,000 EUR and 3 to 6 weeks depending on connector availability for your version.

How long until it goes live?

Between 10 and 16 weeks for a full scope, with a first usable portal version by week six.

What does annual maintenance cost?

Maintenance runs 300 to 800 EUR/month, or 3,600 to 9,600 EUR/year, covering fixes, minor evolutions and support.

Is custom worthwhile versus a vendor?

Yes above 20 to 30 staff, when vendor subscriptions exceed 10,000 EUR/year and your workflow differentiates you commercially.

Let's scope your project. Tell us your file volume, your production tool and the target scope (portal, document management, signature) for a calibrated budget. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.

Tags:#accounting firm software#client portal#document management#document collection#Cegid integration#e-signature#application maintenance#time savings
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Mohamed Bah

Fondateur, Kolonell

Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.